Middle Miocene to recent exhumation of the Slate Range, eastern California, and implications for the timing of extension and the transition to transtension

Abstract

New mapping combined with fault-slip and thermochronological data show that Middle Miocene to recent extension and exhumation of the Slate Range, eastern California, is produced by the active Searles Valley fault system and the Slate Range detachment, an older Middle Miocene low-angle normal fault. Offset Middle Miocene rocks record a combined ~9 km of west-directed extension over the past ~14 m.y. for the fault zones. (U-Th)/He apatite cooling ages of samples from the central and southern Slate Range indicate that footwall cooling began ca. 14 Ma; we interpret this as the age of initiation of motion on the Slate Range detachment. This timing is consistent with inferences made using stratigraphic and structural criteria. Data from the northern Slate Range show that rapid fault slip began along the Searles Valley fault ca. 4 Ma; data from the central and southern Slate Range can be interpreted as indicating cooling at 5-6 Ma. This timing correlates to the results of nearby studies, suggesting a strain transition in the surrounding area between ca. 6 and 3 Ma. The data collected are most consistent with a westward migration in the locus of transtensional deformation, and show that the initiation of that deformation commonly lags the timing predicted by plate reconstructions by a few million years.

Low-temperature thermochronology of the Black and Panamint mountains, Death Valley, California: Implications for geodynamic controls on Cenozoic intraplate strain

“…The new thermochronology data, when placed within the context of published fault timing data, demonstrate that the very eastern part of the Eastern California shear zone experienced a transition to dextral transtension that was coincident with and likely triggered by the plate-boundary kinematic change at 10-8 Ma, while areas to the west lagged this change by several million years. A westward progression in fault initiation is predicted by and may support a rolling hinge model for the structural development of the greater Death Valley area (e.g., Stewart, 1983;Wernicke et al, 1988;Snow and Wernicke, 2000;Niemi et al, 2001;Ferrill et al, 2012), but given the two-phase pattern of deformation documented by this and other studies (e.g., Stockli et al, 2003;Lee et al, 2009;Walker et al, 2014), such a model may be too simplistic. As an alternative, the westward progression of fault initiation could reflect changes in crustal strength that closely follow the locus of earlier extension and crustal thinning (Fridrich and Thompson, 2011).…”

“…3-4 Ma (Fig. 1; Walker et al, 2014;Lee et al, 2009;Stockli et al, 2003). The earlier of these events is linked to Basin and Range extension, while the latter is linked to the initiation of dextral transtension (Stockli et al, 2003;Lee et al, 2009;Walker et al, 2014).…”

“…1; Walker et al, 2014;Lee et al, 2009;Stockli et al, 2003). The earlier of these events is linked to Basin and Range extension, while the latter is linked to the initiation of dextral transtension (Stockli et al, 2003;Lee et al, 2009;Walker et al, 2014). A two-phase history is also supported by differences in the timing, composi-tion, and volume of suites of igneous rocks in the region, with copious intermediate to felsic magmatism during the middle to late Miocene giving way to small-volume mafic eruptions during the Pliocene to Quaternary (e.g., Asmerom et al, 1994).…”

“…geol.ucsb.edu/download/nepac.php, and McQuarrie and Wernicke [2005]). However, timing data from individual structures within the Eastern California shear zone range from middle Miocene to late Pleistocene (see Burchfiel et al, 1987;Hodges et al, 1989;Dokka, 1991, 1993;Holm et al, 1992;Hoisch and Simpson, 1993;Snow and Lux, 1999;Snyder and Hodges, 2000;Niemi et al, 2001;Monastero et al, 2002;Stockli et al, 2003;Guest et al, 2007;Lee et al, 2009;Mahan et al, 2009;Beyene, 2011;Walker et al, 2014), suggesting that the transition from intraplate extension to intraplate dextral transtension may not have been simply related to plate-boundary kinematics, and that other geodynamic factors may have played a role in the temporal and spatial pattern of deformation. One possible factor is lithospheric delamination, which is proposed to have occurred in the central and southern parts of the Sierra Nevada at ca.…”

Evolution of the central Garlock fault zone, California: A major sinistral fault embedded in a dextral plate margin

“…The initiation age is younger in areas west of Death Valley: ca. 4 Ma in Panamint and Searles Valleys (Burchfi el et al, 1987;Hodges et al, 1990;Zhang et al, 1990;Snyder and Hodges, 2000;Walker et al, 2014), and 2-3 Ma farther to the west in Indian Wells Valley . This westward migration of dextral shear possibly also occurred in the Eastern California shear zone, but the initiation ages are poorly known: beginning after 6 Ma (Dokka and Travis , 1990;Schermer et al, 1996;Glazner et al, 2002), 3.8 Ma (Oskin and Iriondo, 2004), or even younger (Miller and Yount, 2002).…”